From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx147.postini.com [74.125.245.147]) by kanga.kvack.org (Postfix) with SMTP id B1ADC6B0062 for ; Thu, 6 Sep 2012 06:44:36 -0400 (EDT) Received: by dadi14 with SMTP id i14so1104955dad.14 for ; Thu, 06 Sep 2012 03:44:36 -0700 (PDT) Date: Thu, 6 Sep 2012 18:44:29 +0800 From: Shaohua Li Subject: [patch 2/2]compaction: check lock contention first before taking lock Message-ID: <20120906104429.GB12718@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, mgorman@suse.de, aarcange@redhat.com isolate_migratepages_range will take zone->lru_lock first and check if the lock is contented, if yes, it will release the lock. This isn't efficient. If the lock is truly contented, a lock/unlock pair will increase the lock contention. We'd better check if the lock is contended first. compact_trylock_irqsave perfectly meets the requirement. Signed-off-by: Shaohua Li --- mm/compaction.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) Index: linux/mm/compaction.c =================================================================== --- linux.orig/mm/compaction.c 2012-09-06 14:46:13.923144263 +0800 +++ linux/mm/compaction.c 2012-09-06 14:46:58.118588574 +0800 @@ -295,9 +295,9 @@ isolate_migratepages_range(struct zone * } /* Time to isolate some pages for migration */ - cond_resched(); - spin_lock_irqsave(&zone->lru_lock, flags); - locked = true; + locked = compact_trylock_irqsave(&zone->lru_lock, &flags, cc); + if (!locked) + goto skip; for (; low_pfn < end_pfn; low_pfn++) { struct page *page; @@ -400,6 +400,7 @@ isolate_migratepages_range(struct zone * if (locked) spin_unlock_irqrestore(&zone->lru_lock, flags); +skip: trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); if (!nr_isolated) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org